Ethernet cables and the familiar RJ-45 Ethernet plugs and jacks that terminate these cables are standard communication links for computer systems, telecommunications systems, etc. These links need to be tested, particularly, in telecommunications applications, where they can be made over very long distances, e.g., spanning the United States and beyond, when they are interspersed with non-Ethernet links, such as, e.g., optical links. Therefore, Ethernet cable testing is critical to pre-determine that all Ethernet cable connections are good in a given communication path through one or more networks.
After that determination is made, a suite of tests can be run, such as those in accordance with International Telecommunications Union Request for Comments 2544 (ITU-RFC-2544). These tests can determine various parameters for that total communication path including its Ethernet cable connections, such as throughput (to determine the quantity of traffic that can be handled), latency (to determine how long it takes to send a signal round-trip), frame loss (to determine if buffers can handle the traffic load without dropping frames), etc.
To this end, Ethernet test-sets, which can be configured as hand-held devices, are commercially available. To determine if the Ethernet connections are good, test signals are sent out from one Ethernet port in the test-set and make a round trip back to the test-set. But, in accordance with the design of these test-sets, the returned test signal cannot be received or accepted in the same test-set port from which the signal was sent. A second Ethernet port is available on the test-set to accept the return signal. Therefore, a dedicated return path connecting to this second Ethernet port must be provided, if that is possible to do under the particular testing constraints involved in a particular test. When the distances involved are great, a separate, dedicated Ethernet cable return path is usually not feasible.
Moreover, if there is only one Ethernet port in the network node/element at the far-end of the test path available for test purposes, a separate, dedicated return path would then be unavailable. If a technician jumpers the test signal within the pins of that one available Ethernet port (from transmit pins to receive pins) to return the test signal to the test-set along a path similar to that from which it came, the test fails because the signal ultimately returns to the same Ethernet port on the test-set from which it was sent which is not accepted by the test-sets.